1. Field of the Invention
The invention relates to a control apparatus and control method for a vehicle, for changing a shift speed of a stepped automatic transmission based on a vehicle state such as a value corresponding to a driving force required for a vehicle, according to a pre-stored shift pattern for deciding a shift speed of the stepped automatic transmission. More particularly, the invention relates to a technology in which multiple shift patterns are provided, and one shift pattern is selected from among the multiple shift patterns.
2. Description of the Related Art
Generally, an operation of an automatic transmission is controlled such that a shift speed, which is decided based on an actual accelerator pedal operation amount or an actual vehicle speed, is achieved according to a shift diagram (shift map) stored in advance using an accelerator pedal operation amount (or a throttle valve opening amount) and a vehicle speed as parameters, that is, a so-called shift pattern. An example of such a technology is realized in a vehicle disclosed in Japanese Patent Laid-Open Publication No. 2002-187460. Meanwhile, a vehicle disclosed in Japanese Patent Laid-Open Publication No. 07-277038 is known in which control of a shift speed and engine torque (hereinafter, referred to as “driving force demand control” is performed such that more appropriate driving force can be obtained by using a driving force required for the vehicle as an accelerator pedal operation amount, which is one of the parameters for setting the shift pattern. The driving force required for the vehicle (hereinafter, referred to as the “required driving force” where appropriate) is calculated based on a vehicle state such as the accelerator pedal operation amount or whether the vehicle is running on an uphill/downhill road.
However, when a shift speed at which the required driving force can be obtained is selected, an engine rotational becomes a speed in a high rotational speed region. As a result, drivability may deteriorate due to a sense of discomfort felt by a driver, fuel efficiency may be reduced, and an amount of toxic exhaust gas (CO2, NOx and the like) may increase. On the other hand, when a shift speed, that is higher than the shift speed at which the required driving force can be obtained, is selected such that the engine rotational speed does not become a high rotational speed, the required driving force may not be able to be obtained and the vehicle may not be able to be driven in an intended manner.